1. Field of the Invention
The present invention relates to a receiver suitable for lightwave applications.
2. Description of the Prior Art
Optical transmission systems are finding use in a wide variety of applications that once relied on metallic conductors or radio links. For example, closed-area television (CATV) systems are now being implemented with optical fibers instead of coaxial cables. To allow for the transmission of a large number of channels with minimum bandwidth and at low cost, amplitude modulation (AM) or other analog techniques may be used for modulating the optical signal. When receiving the AM signal, low distortion amplifiers are required. These typically use a balanced amplifier configuration to cancel second-order non-linearities. For example, the amplifier circuit of a typical trunk amplifier used in analog CATV lightwave systems is shown in FIG.3. A p-i-n photodiode can be connected to the amplifier input transformer, as shown, to form an optical receiver. However, a disadvantage of this input connection using a transformer is that the transformer has considerable loss, which may limit the noise figure of the receiver. Furthermore, the loss increases at very high and very low frequencies, thereby limiting the bandwidth.